One-side back bead forming butt-welding process using a thermosetting backing composite

ABSTRACT

A powdery backing composition for use in a one-side back-beadforming butt-welding process wherein a powdery backing composition is applied against the underside of the groove between workpieces to be welded together and said workpieces are butt-welded on the upperside of said groove, said backing composition including thermosetting resin powder, iron powder, and slag forming agent and having been initially agglomerated by the melting of said resin powder prior to the welding operation.

atent 1 Arikawa et a1.

ONE-SIDE BACK BEAD FORMING BUTT-WELDING PROCESS USING A THERMOSETTINGBACKING COMPOSITE Inventors: Masayasu Arikawa; Katsuro -lio,

both of Fujisawa, lapan Assignee: Kobe Steel Ltd., Kobe, Japan Filed:Aug. 13, 1970 Appl. No.: 63,643

Related U.S. Application Data Division of Ser. No. 657,197, July 31,1967, Pat. No. 3,548,489.

Foreign Application Priority Data 1 May 8, 1973 [56] References CitedUNITEDSTATES PATENTS 2,320,700 6/1943 Kent et al. ..228/50 X 2,331,68910/1943 Hodge ..29/491 2,441,176 4/1948 Wilson et al.... ..228/50 X2,558,411 6/1951 Austin et al. 106/63 3,002,272 10/1961 Hodges ..29/4912,294,439 9/1942 Bagley ..228/50 X 2,331,937 10/1943 Schreiner ..228/50X Primary Examiner-J. Spencer Overholser Assistant ExaminerRobert J.Craig Attorney-Wenderoth, Lind & Ponack [57] ABSTRACT A powdery backingcomposition for use in a one-side back-bead-forming butt-welding processwherein a powdery backing composition is applied against the undersideof the groove between workpieces to be welded together and saidworkpieces are butt-welded on the upperside of said groove, said backingcomposition including thermosetting resin powder, iron powder, and slagforming agent and having been initially agglomerated by the melting ofsaid resin powder prior to the welding operation.

2 Claims, 4 Drawing Figures PATENTEDHAY am INVENTORS ndwha gq fri I M WBACKGROUND OF THE INVENTION In one of the prior art butt-weldingprocesses for relatively large and/or thick steel workpieces, generally,two steel workpieces are first aligned edge to edge leaving apredetermined space or groove between their opposite edges where metalis to be deposited and a welding operation is performed on the uppersideof the groove. After the upperside of the groove has been welded, theworkpieces are then reversed so as to make the yet-to-be weldedunderside of the workpieces the top and thereafter, the workpieces arewelded on the present upperside of the groove repeating the sameprocedure which was followed in welding the first upperside of thegroove. However, the reversing of such heavy workpieces in the course ofthe welding operation is rather troublesome and this fact presents agrave impediment to the automation of various processes for weldinglarge size and/or thick workpieces.

In building or assembling ships, bridges, storage tanks and the likehuge structures, the so-called one side butt welding process has beenproposed and practiced by some people in the industry. According to thisprocess, steel plates are welded on only one side thereof so as to formback beads on the other or opposite side of the workpieces. However,such a welding process has been exclusively performed by directing thewelding rods downward. At present, when the welding operation isperformed along curved sections of workpieces and the upward weldingoperation is performed, a combination of gouging and back bead formingwelding has been relied upon. Although the oneside back-bead-formingwelding process has been practiced by some people in the industry forwelding curved sections of workpieces or welding the workpieces from thelower portions to the upper portions thereof with the use of handwelding rods for back-bead forming, such process has presented variousproblems, for example, it is difficult to obtain precisely definedgrooves between workpieces, proper seams of beads, and skilled workers,and therefore, the process has not been yet commonly and widelypracticed in the-industry.

Of late, improved side butt-welding processes for relatively largeand/or thick steel workpieces have been developed. In one of these newlydeveloped one side butt-welding processes, as a preparatory step, twosteel workpieces are aligned edge to edge with a space or groove formedbetween their opposite edges where metal is to be deposited and a copperalloy backing block is applied against the underside of the workpiecesat the bottom of the groove and then, the workpieces are butt-weldedfrom the upperside of the groove. In another newly developed one sidebutt-welding process, two steel workpieces are aligned in the manner asdescribed above and a suitable powdery backing composition is disposedon the underside thereof at the bottom of the groove and then theworkpieces are butt-welded from the upperside of the groove. However,both of these newly developed one side butt-welding processes haveinherent disad vantages; that is, in the one side butt-welding processusing the copper alloy backing block, if there is any clearance orclearances between the steel workpieces and the backing strip, moltenmetal flows into the clearance or clearances and a fin or fins arecaused to form in the clearance or clearances and in addition, slag maybe incorporated into the molten metal.

Furthermore, since both the steel workpieces and the copper alloybacking strip are rigid bodies, if the workpieces have ragged portionsand/or curvatures on their underside the backing block often does notcontact the underside of the workpieces to be welded together evenly. Inaddition, should the copper alloy backing block be a grooved block,there is the possibility of insufficient depth of penetration due toflow of molten metal into the groove of the backing block and formingmetal deposits, overlaps, undercuts and the like in the backing blockgroove.

On the other hand, the one side butt-welding process using the powderybacking composition is superior in some aspects to the one sidebutt-welding process using the copper alloy backing block, but even whenthe powdery backing composition-type one side butt-welding process isemployed, it is not easy to at all times insure that the backingcomposition can positively and uniformly contact at all the points ofthe underside of the workpieces.

SUMMARY OF THE INVENTION The present invention relates to a powderybacking composition for use in one side butt-welding processes for steelworkpieces, and more particularly large size and/or thick steelworkpieces such as parts of vessels, buildings, bridges and other steelconstructions. Such steel workpieces which are aligned edge to edge witha groove formed between their opposite edges and with a backingcomposition disposed at the bottom of the groove and held against theworkpieces by means of a supporting member are welded from theirupperside.

One object of the present invention is to provide a powdery backingcomposition for use in a one-side back-bead-forming butt-welding processwhich can be applied to both curved surface welding and upward weldingas well as to downward welding.

Another object of the present invention is to provide a powdery backingcomposition for use in a one-side back-bead-forming butt-welding processwhich, when applied to downward welding, can be performed with the useof jigs and devices which are lighter in weight and smaller in size thanthose which were necessary for any prior art one-side back-bead-formingbutt-welding process.

Another object of the present invention is to provide a powdery backingcomposition for use in a one-side back-bead-forming butt-welding processin which,

when applied to curved surface and upward welding,-

the process can be performed without the necessity for precisely forminga groove between workpieces and for high degree of skill on the part ofworkers but can form a smooth and continuous back bead.

A further object of the present invention is to provide a powderybacking composition for use in a oneside back-bead-forming process inwhich even when any irregular groove between workpieces is welded, thereis no possibility of deposit metal falling and/or dripping down from thewelded groove.

A further object of the present invention is to provide a powderybacking composition for use in a oneside back-.bead-forming butt-weldingprocess in which even'when the workpieces are weldedfrom only one side,a satisfactory back bead appearance can be obtained and a backing blockwhich upholds a backing composition in contact with thev underside ofworkpieces can be protected from an electric are.

A further object of the present invention is to provide a powderybacking composition which is able to be positively held against theworkpieces when the upward and curved surface welding operations areperformed on the workpieces.

The welding process employing the powdery backing composition of thepresent invention is distinguished from the prior art butt-weldingprocesses in which steel workpieces aligned to be joined together arepreheated and then a backing composition which has been held against theunderside of the workpieces at the bottom of thegroove between theworkpieces in a powdery form is heated so as to have the compositionsolidify and positively adhere to the workpieces. In the welding processemploying the powdery backing composition of the present invention it isnot necessary to preheat the workpieces. A novel powdery backingcomposition of the present invention contains a slag forming agent,thermosetting resin powder and iron powders and it is applied againstthe underside of the steel workpieces at the bottom of the groovebetween the workpieces and firmly held in position by a backing blockwhich holds the composition up from the bottom. Thereafter, an electricarc welding operation is initiated from the upperside of the workpiecesalong the groove or weld line.

The composition of the present invention is applicable to the one-sidebutt-welding of steel work pieces of any chemical composition, anythickness and/or sizes; that is, the workpieces may be carbon steels orsteel alloyshaving different chemical compositions and varyingthicknesses and/or sizes. In addition, in such welding the weld line orgroove where metal is to be deposited bythe butt-welding may bestraight, curved or any combination of curved and straight sections. Andthe welding position may be horizontal, vertical or slanted. However,the opposite edges of workpieces to be butt-welded preferably form abeveled groove which has a V-section, a Y-section or an I-se ction. Thegrooves need not have an open bottom or root, but an opening up to mm atthe bottom or root of the groove is workable. In some cases, theworkpieces to be welded together may be of different thicknesses, or theworkpieces may be laid and welded at different heights from each up to 3mm. The backing block to be employed in performing the process employingthe composition of the present invention may be and is usually formed ofa aluminum, aluminum alloys, copper or copper alloys. The backing blockfor such welding preferably has as small a thickness as possible and thethickness of the backing block is selected depending upon the length ofthe weld line between the workpieces to be butt-welded. Theconfiguration of the backing block is also determined in conformity withthe specific configuration of the weld line (straight or curvedconfiguration). The backing block may be a plain plate or a plate havinga longitudinal groove on one side extending along the direction in whichthe weld line extends when the block is applied on the underside of theworkpieces. Thus, the groove formed on the backing compositionsupporting side on the backing block can conveniently receive a backingcomposition thereon. The groove to be formed on the backing block sidehas capacity enough to receive a predetermined amount of a backingcomposition which may be determined depending upon specific factorsinvolved in the butt-welding operation to be performed, but usually thebacking block groove is shallow and wide. The upper edges of theopposite side walls. of the backing block groove are preferably inwardlybent so that the backing composition will not come out of the groove.

The slag forming agent to be contained in the backing compositionemployed is not limited to only an agent which has a specific grainsize, but may be any one selected from those which have beenconventionally employed as the slagforming agents in the conventionalbacking compositions for welding purposes. The slag forming agents to beemployed the backing composition in may be fluxes which have beencommonly employed for conventional welding. One typical prior art fluxis comprised of oxides such as SiO A1 0 TiO ZrO MgO, CaO and BaO in apowdery form, halide such as CaF in a powdery form, metallic carbonatessuch as CaCO BaCO and MgCO in a powdery form and Fe, Fe-Si, Fe-Mn, Fe-Tiand Fe-Al in a powdery form. The above flux or slag forming agent ispreferably employed in at least 9 percent by weight based on the weightof the total backing composition. Preferably, iron powder is also addedto the backing composition in a suitable amount. The amount of ironpowder to be added to the backing composition may vary within a range of10 percent by weight based on the weight of the total backingcomposition and in some cases the additive iron powder may be in a formof an iron alloy containing another metallic constituent orconstituents. As the welding operation proceeds, the additive ironpowder in the backing composition forms a wave-shaped back bead line atthe bottom of the groove being welded while the slag forming agent inthe same backing composition gives a fine appearance to the surface ofthe thus formed wave-shaped back bead line.

As the welding operation proceeds, the additive iron powder meltstogether with the slag forming agent within the backing composition andthe molten iron powder forms a wave-shaped back bead line on theunderside of the workpieces along the bottom of the weld line or groovebeing welded. The supply of metal from the molten backing composition isquite effective in carrying out the novel one side back bead formingbuttwelding process because the molten iron powder merges into themolten metal from the other constituents of the backing composition andthereby the amount of metal deposited on the workpieces is increased.

' As pointed hereinabove, by employing the novel backing compositionwith the use of the present invention, with the use of large and/orthick steel workpieces can be butt-welded from just the upper sidethereof with the backing composition held against the opposite orunderside of the workpieces without the necessity for reversing theworkpieces because the molten backing composition is a binding agentwhich melts and solidifies the other principal backing compositionconstituents when the resin is heated to a temperature up to 450C.Examples of the binding agents to be employed in the backing compositionare phenol resin,

epoxy resin and isocyanate. The temperature to which the thermosettingresin is heated is limited to 450C because, if the thermosetting resinis heated above the specified temperature, the organic ingredient oringredients of the resin are carbonized whereby the flux solidified bythe resin or binding agent may be rendered fragile. The amount of theresin to be employed as the binding agent for the principal constituentsof the backing composition can not be strictly defined by any numericalvalue; it can be merely said that the resin may be used in an amountsufficient to solidify the principal backing composition constituents.When the binding agent is a thermosetting resin, generally, the amountof the binding agent is preferably within the range of 0.2 to 4.0percent by weight based on the weight of the total backing composition.

While the backing composition of the present invention is primarilyintended to be used in a powdery form received in the groove on thebacking block and to be solidified as the welding operation progressesto provide a satisfactory back head, the solidification being effectedby the heat generated by the welding process, the backing compositionreceived in the groove on the backing block may be heated before thewelding operation is initiated or during the welding operation asdesired.

When the backing composition is heated during a welding operation, theheat generated by the welding operation is utilized as the heat sourcefor solidifying the backing composition. In this case, the backingcomposition is preheated by the heat transferred from a point in thegroove where the welding was initiated whereby the resin content in thebacking composition is first melted so as to render the principalpowdery backing composition constituents into an agglomerated statewhereupon the whole backing composition can firmly adhere properly anduniformly to the workpieces to be joined together, following the contourof the workpieces being welded resulting in a decrease of the formationof fines attributable to the flowing out of molten metal and in theformation of a uniform waveshaped back bead on the underside of theworkpieces at the bottom of the groove.

Furthermore, since the powdery backing composition has been previouslyagglomerated as a result of the melting of the resin powder contained inthe backing composition, the composition can be effectively compressedby the weight and expansive force of an air hose which is disposedwithin the groove in the backing block over the backing composition whenthe hose is supplied with compressed air, and as a result, the backingcomposition is caused to agglomerate just before the welding ofworkpieces thereby ensuring close contact of the composition with theworkpieces and preventing fins from being formed on the weld. Inaddition, the formation of the slag is effective in providing a quitesmooth and uniform wave-shaped back bead line.

The final pass which is to be performed on the topside groove incarrying out the one-side butt-welding process may be made by any of theconventional processes-hand welding, semi-automatic welding, andautomatic welding (carbonic acid gas-shielded welding,

I inert gas-shielded welding, sub-merged arc welding,

electro-slag welding and non-shielded welding), but in any of theabove-mentioned processes the welding rod to be employed should be aconsumable wire electrode. The above-mentioned various welding processesmay be suitably selected depending upon the welding conditions such asvoltage, amperage and velocity.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 through 4 are fragmentaryviews in section illustrating different arrangements with which theoneside back-bead-forming butt-welding process employing the backingcomposition of the present invention is carried out.

PREFERRED EMBODIMENTS OF THE INVENTION Referring now to the Figs. of theaccompanying drawings, and more particularly to FIG. 1 thereof, twosteel workpieces 2 and 2 having opposing bevelled edges are shown asbeing aligned edge to edge in the same plane so as to define a Y-shapedgroove G between their opposing bevelled edges. A suitable backingcomposition 3 is disposed on the underside of the workpieces 2 rightbelow the groove G covering an area at and in the vicinity of the bottomof the groove. The backing composition 3 is held against the undersideof the workpieces 2 and 2 from below by means of a suitable backingblock 1 which is in turn upheld by a conventional base constructiondisposed below the block (not shown). Thus, it will be understood thatthe backing composition 3 is held in position in a compressed conditionbetween the workpieces 2 and 2 and the supporting unit comprising thebacking block 1 and conventional base construction by the weight of theworkpieces and the cooperating supporting action of the upholding unit.

When it is desired to obtain a more positive or effective contact of thebacking composition 3 with the workpieces 2 and 2, the arrangement asshown in FIG. 3 is preferably employed. In this arrangement, the backingblock 3 is formed on the upper surface thereof with a longitudinalrecess 4 which extends along the bottom of the groove G when the backingblock is disposed on the underside of the. workpieces and an air hose oran air bag 5 is disposed within and along the longitudinal recess 4. Thebacking composition 3 is filled within the block recess 4 over the airhose 5. With this arrangement, when the air hose 5 is supplied withcompressed air from a suitable compressed air supply source (not shown),so as to expand the hose, the expanded air hose 5 pushes up andcompresses the backing composition 3 against the workpieces 2 and 2whereby thepushed-up and compressed backing composition 3 can bepositively abutted against the underside of the workpieces 2 and 2 atthe bottom of the groove G resulting in close contact of the compositionwith the workpieces. The arrangement. of FIG. 3 is particularlypreferable when the workpieces 2 and 2 are relatively great in thicknessand light in weight. If the one-side butt-welding process is carried outwhile the workpieces 2 and 2 are advancing through the welding stationin a welding system, an arrangement as shown in FIG. 4 is employed. Insuch an arrangement, an endless belt 6 is employed in place of thestationary backing block 1 shown in FIGS. 1 through 3. A lower backingcomposition receiving or guide member 7 and an upper scraper 8 areprovided in the vicinity of one or the inlet end of the belt 6. Abacking composition feeder 9 in a screw form is provided on the side ofthe receiving member 7 opposite the belt 6.

With the above arrangement, when the feeder 9 is operated or rotated bya suitable conventional drive means (not shown), the feeder 9continuously feeds the backing composition 3 upward in a controlled ratethrough the receiving member 7 onto the moving belt 6. The backingcomposition 3 may be conveyed on the belt 6 in a controlled amount orthickness and therefore, a constant or controlled thickness of backingcomposition layer is at all the times present between the workpieces 2and 2 and the belt 6. Thus, the buttwelding process can be automaticallycarried out by manipulating a welding torch 10 disposed in a suitableoperative position with respect to the workpieces while the workpiecesare advancing through the welding station.

The following are examples in which the one-side back-bead-formingbutt-welding process were successfully carried out by employing thepowdery backing composition of the present invention.

EXAMPLE 1 Two 400 X 600 mm steel workpieces were cut from a killed mildsteel plate stock having a thickness of 32 mm and one edge of eachworkpiece was bevelled so as to form a Y-shaped groove (50) having adepth of mm when the workpieces are aligned with their bevelled edgesfacing each other. The workpieces were placed on a backing block with abacking composition interposed between the workpieces and the backingblock as shown in FIG. 1.

The backing composition employed comprised the following constituents byweight percentage:

Sub-merged arcwelding flux (G. 20) 43.0% Iron powder (less than mesh)35.0% F errosilicon 17.5% Phenol resin powder 4.5%

The above-mentioned backing composition was spread over the backingblock in a width of 60 mm and a thickness of 25 mm at and in thevicinity of the bottom of the groove between the workpieces. Using alength of mild steel wire electrode having a diameter of 6.4 mm ('U.S.43) and sub-merged arc welding flux (P.F.1l. 45, 1O 48 mesh), a tandemwelding operation was performed in accordance with the conventionalsub-merged arc welding process.

The welding conditions were:

Leading pass 1200 A X (30 34)V X 30 cm/min.

Trailing pass 1 300 A X (34 36)V X 30 cm/min. X-ray examination of thebutt-welded portion or metal deposited portion of the workpiecesindicated that the metal deposit was of a first grade quality whendetermined in accordance with 118 criteria. The waveshaped back beadline was smooth and uniform having a width of 12 mm and a height of 1.5mm and no slag was found in the back bead. In addition, no undercutswere found in the back bead line.

TABLE The constituents of Flux G. 20 and Flux P.F.H. 45 (by weight p G.20 P.F.I-l. 45 SiO, 54.52 20.0 Al,0, 3.81 10.0 FeO 1.03 trace TiO, 0.20trace CaO 31.82 20.0 MgO 9.24 40.0

The invention has been describedin detail with particular reference topreferred embodiment thereof, but

it will be understood that variations and modifications can be effectedwithin the spirit and scope of the invention.

' What is claimed is:

1. A weld backup means for a one side back-beadforming butt-weldingprocess comprising a powdery. backing composition consisting of amixture of a conventional powder welding flux, thermosetting resin andiron powder, said thermosetting resin being within the range of 0.2 to4.0 percent by weight based on the total weight of the composition, saidconventional flux being over 9 percent by weight based on the totalweight of UNITED STATES PATENT AND TRADEMARK OFFICE Certificate Patent N0. 3,731,868 Patented May 8, 197 3 Masayasu Arikawa and Katsuro IioApplication having been made by Masayasu Arikawa and Katsuro Iio, theinventors named in the patent above identified, and Kobe Steel Ltd,Kobe, Japan, the assignee, for the issuance of a certificate under theprovisions of Title 85, Section 256, of the United States Code, addingthe names of Motomi Kano and Naoki Okuda as joint inventors, and ashowlng and proof of facts satisfying the requirements of the saidsection having been submitted, it is this day of June 24, 1975,certified that the names of Motomi Kano and N aoki Okuda are herebyadded to the said patent as joint inventors with the said MasayasuArikawa and Katsuro Iio.

FRED W. SHERLING, Assocwktte Solicitm".

2. A weld backup means as claimed in claim 1, wherein said iron powderis included in an amount of 10 to 90 percent by weight based on thetotal weight of the composition.